Method of melting titanium



United States Patent 3,493,363 METHOD OF MELTING TITANIUM Paul J. Ahearn, Belmont, Mass., assignor to the United States of America as represented by the Secretary of the Army No Drawing. Filed Apr. 25, 1966, Ser. No. 545,806 Int. Cl. C22c 15/00; C22b 9/00; C22d 7/06 US. Cl. 75-10 3 Claims ABSTRACT OF THE DISCLOSURE Method of melting titanium or titanium alloy in which the inner ceramic walls of an induction furnace are packed with powdered barium fluoride to form a lining, a mass of titanium is centered within the fluoride lining, and the titanium is heated by induction. The fluoride adjacent the heated titanium is first melted by the outward flow of heat induced in the titanium, and then the titanium melts and remains centered in the fluoride due to the density of the fluoride and to the influence of the induction field of the furnace coil which produces a stirring effect in the molten titanium. The fluoride lining prevents contact of the titanium with the crucible walls.

The invention described herein may be manufactured and used by or for the government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to the melting of titanium and titanium alloys.

The problem of making good quality titanium or titanium-alloy ingots is a diflicult one but the solution would be greatly facilitated if a suitable refractory container could be found for molten titanium. The reason for the difficulties encountered in the melting and/ or casting of titanium, is that the metal has a very high melting point and when molten reacts with virtually everything with which it comes in contact. All oxide refractories are reduced by contact with the molten titanium metal which is then contaminated by both the oxygen and the contained metallic element and the product is thereby embrittled. Tests reveal that melts made in a high frequency induction furnace using refractory metals such as tungsten, molybdenum and tantalum, show that large quantities of these metals were dissolved in the titanium. Obviously all of these metals are adequately refractory but their solubility in the titanium melt is high and their solution rate is rapid.

It is therefore, the object of this invention to employ a material that will contain the titanium or titanium alloy in a molten state and one that is insoluble therewith.

In the search for a material in which titanium may be melted, it has been found that certain chlorides and fluorides are stable in the presence of titanium and could be considered as possible material for crucibles or containers for molten titanium. However such candidate materials have a melting point below that of molten titanium which presents an obstacle to satisfactory operation. This obstacle may be turned into a solution of the problem for containing molten titanium by employing powdered chlorides or fluorides that have a lower melting point but do not react with titanium, by permitting the powdered material to melt and thereafter form a liquid container that will also contain the molten titanium without mixing physically or chemically.

In operation, since thermodynamic calculations indicate that titanium does not react with barium fluoride, the molten titanium is contained within a liquid fluoride, such as barium fluoride, by utilizing a conventional induction melting furnace and packing the walls of the ice.

ceramic crucible or container with powdered barium fluoride. The titanium or titanium alloy is placed in the center of the fluoride-lined container and the heat induced in the titanium will change the fluoride liner to a molten mass with unmelted titanium remaining in the center thereof. As the heating is continued the titanium is melted and remains centered in the molten barium fluoride due to the difference in surface tension of the two materials and, the influence of the field coil of the induction furnace. Thereafter, the titanium which remains centered as a molten unit, may be drawn off the furnace in an uncontaminated condition.

Barium fluoride was selected as a liquid container not only because of its favorable thermodynamic relationship with titanium but also because its density is approximately the same as that of titanium and these factors offer additional assistance in maintaining the molten titanium centered within the fluid bath.

Other fluorides and chlorides, which meet the same requirements as barium fluoride, are considered adequate for the purposes of this treatment.

In the foregoing, the preferred embodiment of this invention has been disclosed. However it is not intended that this invention be so limited to the specific example set forth, as it will be apparent to those skilled in the art,'that various chlorides and fluorides may be employed without departing from the spirit of the invention or exceeding the scope of the appended claims.

What is claimed is:

1. The method of melting titanium or a titanium alloy which comprises, packing the inner ceramic walls of an induction furnace with a powdered barium fluoride to form a lining, centering the titanium compound within the compressed lining, heating by induction the titanium or titanium alloy sufliciently to melt the lining to form a molten bath adjacent the titanium, continuing the heating to melt the titanium or titanium alloy which remains centered due to the influence of the induction field of the furnace coil and drawing off the titanium from the molten bath.

2. A method of melting titanium or a titanium alloy which comprises, packing to form a lining of the inner ceramic walls of an induction furnace with a powdered fluoride having a lower melting point than titanium and of approximately the same density, centering the titanium or titanium alloy within the compressed lining, inducing sulficient heat in the titanium compound to first melt the compressed lining to form a molten bath adjacent the titanium, continuing the heating to melt the titanium compound which remains centered in the molten bath due to the influence of the induction field of the furnace coil and drawing off the molten titanium which remains separate from the molten lining due to the difference in surface tension.

3. A method of melting titanium or a titanium alloy as claimed in claim 2, wherein the powdered fluoride for the lining is barium fluoride.

References Cited UNITED STATES PATENTS 574,068 12/1896 Manhes -95 XR 3,417,808 12/1968 Rosenberg 7S65 X FOREIGN PATENTS 808,843 9/ 1956 Great Britain.

L. DEWAYNE RUTLEDGE, Primary Examiner I. E. LEGRU, Assistant Examiner US. Cl. X.R. 

